1. Field of the Invention
The present invention relates generally to the field of semiconductor technology. More specifically, it relates to one-time electrically programmable antifuse technology for use in field programmable logic applications. Still more specifically, the present invention is directed to a novel antifuse and method of fabricating such a novel antifuse.
2. The Prior Art
Numerous processes for the fabrication of antifuses are known in the art. Some of these processes may easily be integrated into already existing integrated circuit fabrication processes. Some antifuse elements incorporate a dielectric antifuse material which contains a nitride or oxide material such as silicon nitride ("SiN") or silicon dioxide ("SiOi.sub.2 "), either as a single layer, or as a part of a multilayer dielectric such as those described in U.S. Pat. No. 4,823,181 to Mohsen et al., entitled PROGRAMMABLE LOW IMPEDANCE ANTIFUSE ELEMENT and U.S. Pat. No. 4,899,205 to Hamdy et al., entitled ELECTRICALLY-PROGRAMMABLE LOW-IMPEDANCE ANTI-FUSE ELEMENT. Such antifuse structures exhibit excellent leakage and reliability characteristics, and are thus preferred for user-programmable antifuse applications.
Polysilicon ("Poly")/Oxide-Nitride-Oxide("ONO")/N+ diffusion antifuse has long been a primary choice for production antifuse structures. Essentially it consists of a top electrode formed of Poly, an antifuse material layer consisting of a sandwich of SiO.sub.2, SiN, and SiO.sub.2 and a lower antifuse electrode consisting of an N+ diffusion region. Unfortunately, as the demand for higher density devices and, hence, a smaller antifuse structure forces the construction of smaller antifuses, this process has not proved highly scalable in both the antifuse material layer thickness (which determines breakdown or programming voltage of the antifuse) and the width of the antifuse cell. This is manifested as follows: when the active antifuse cell opening is enlarged, the defect density of the product with the same antifuse population increases. The defect density of the product also increases when the antifuse thickness is shrunk and the bottom oxide of the antifuse is grown over the N+ diffusion area. The present invention is directed toward reducing the problems arising from the scaling down of current ONO-based antifuse technology and providing the needed performance and reliability for next generation antifuse process.